In a chronically instrumented dog, the following projects are in progress or will be initiated: (1) To ascertain whether increases in cardiac output found in a shock avoidance paradigm in contrast to those found during exercise are excessive with respect to any increases in oxygen consumption. (2) Using the same experimental paradigms, to ascertain if changes in renal functioning are more appreciable modified by the behavioral stressor than exercise. (3) To ascertain the validity and sensitivity to sympathetic influences on myocardial performance of intraventricular and intra-aortic dP/dt. In young adult normotensives and/or borderline hypertensives, the following projects are in progress or will be initiated (1) To ascertain the sensitivity of pulse propagation time (PPT) to sympathetic influences on myocardial performance and whether PPT can be used as a non-encumbering technique to assess the lability of systolic blood pressure during naturalistic field stressors. This project also involves determining the influence of systolic time intervals on PPT. (2) To determine why stressors which provide some opportunity to control or cope with, in contrast to stressors which provide no opportunity to control, evoke beta-adrenergic effects on the myocardium and vesculature (3) To ascertain in labile hypertensives and individuals with a family history of hypertension whether they are more beta-adrenergically reactive to certain stressors. (4) To initiate a project to determine if such beta-adrenergic reactivity has prognostic value with respect to the future development of hypertension. (5) To ascertain if beta-adrenergic reactivity is associated with certain aspects of life style.